Well, today it's very easy to surpass Skriabin's original idea, since in 1910 the technology was very limited.
If you're wanting to know about the actual design of such a thing, it could by anything from a keyboard activating low voltage relays which would lit whatever, from LEDs to high voltage lights to fiber optics to lasers. You're only limited by your budget and imagination.
Personally, I would go much further than just mere switches as activators. You could take a MIDI keyboard and design a custom MIDI decoder that would use logical gates to transpose the MIDI notes into not only the 12 colors of each key forming an octave, but variations of colors according to which octave the keys are played, etc.
Jean-Michel Jarre build a laser harp around 1980 for his world concerts, which isn't so far from Skriabin's idea.